This Microsoft Support article “How to manage .pst files in Outlook 2007, in Outlook 2003, and in Outlook 2002” is the best knowledge base article that I know about.
This article describes how to use personal storage folders, also known as .pst files, to back up data that you created in Microsoft Office Outlook 2007, Microsoft Office Outlook 2003, and Microsoft Office Outlook 2002. You can back up messages, contacts, appointments, tasks, notes, and journal entries in .pst files.
If you know about other great Outlook resources, please comment.